Splat-cooled fe-co-v and fe-co-cr alloys and devices using same

ABSTRACT

AN INDUCTIVE T HERMOMETER IN WHICH THE INDUCTOR CORE CONSISTS OF A SPLAT COOLED ALLOY OF EITHER THE FE-CO-V OR THE FE-CO-CR SYSTEMS, BOTH OF WHICH HAVE BEEN FOUND TO EVIDENCE PARAMAGNETIC PROPERTIES AT ROOM TEMPERATURES AND FERROMAGNETIC PROPERTIES UPON COOLING TO 1.4*K.

0d 216 1971 E. A. NESBITT ErAL n 3,614,893

SPLAT-COOLED I"e-C0-V AND FG-CtJ-C ALLOYS AND ADEVICES USING SAME Filed om.L 25, 1967 2 sheets-sheet 1 F/G. l,

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l Life-,Q c0/ F/G.3 (n e L 40 LU 2o [L h *r o d '-0.5 1 i I l o loo 20o (305) 40o TEMPERATURE "K RH. WILLEMS ATTORNEY Oct 26, .1971 E. A. NE'SBITT EVAL -sPLAT-cooLED Fe-Co-v AND F-Co-c'r ALLoYs AND DEVICES USING SAME Filed Oct'. 25, 1967 2 Sheets-Shoot 2 METER States Patent 3,614,893 Patented ct. 26, 1971 3,614,893 SPLAT-COOLED Fe-Co-V AND Fe-Co-Cr ALLOYS AND DEVICES USING SAME Ethan A. Nesbitt, Berkeley Heights, and Ronald H.

Willens, Warren Township, Somerset County, NJ., assignors to Bell Telephone Laboratories, Incorporated, Murray Hill, NJ.

Filed Get. 23, 1967, Ser. No. 677,312 Int. Cl. 601k 7/38 U.S. Cl. 73--362 R 2 Claims ABSTRACT 0F THE DISCLDSURE An inductive thermometer in which the inductor core consists of a splat cooled alloy of either the Fe-Co-V or the Fe-Co-Cr systems, both of which have been found to evidence paramagnetic properties at room temperatures and ferromagnetic properties upon cooling to l.4 K.

This invention relates to alloys of the iron-cobalt system. More particularly, the present invention relates t0 splat-cooled alloys of the iron-cobalt system and to devices utilizing such compositions.

In recent years considerable interest has been generated by workers in the metallurgical arts in a technique termed splat-cooling which involves rapid cooling of alloys from the liquid state, so resulting in the (a) formation of metastable phases and the concomitant extrapolation of solubility limits beyond their equilibrium values, (b) attainment of new phases not previously observed under equilibrium conditions, and (c) formation of amorphous alloys.

In accordance with the present invention, the splat-cooling techniques has been utilized for the preparation of alloys in the iron-cobalt system including critical percentages of either vanadium or chromium, which surprisingly behave paramaguetically at room temperature and ferromagnetically at temperatures of the order of 1 K. This unique behavior may be attributed to the presence of superparamagnetic particles, which due to size variation and density transfer continuously and reversibly to single domain ferromagnetic particles as the temperature is lowered, and serves as the basis for incorporation of the described compositions as the core material of inductors. The resultant structures evidence a large temperature coeliicient of inductance as the magnetic permeability continually changes from approximate unity when the composition is entirely paramagnetic to the initial permeability of the fully magnetic state. It follows from this discovery that this property may be utilized in a temperature transducer wherein the inductance of a coil containing the splat-cooled alloys of the invention may be measured as a function of temperature.

The invention will be more readiy understood by reference to the following detailed description taken in conjunction with the accompanying drawing, wherein:

FIG. l is a front elevation View in cross-section of an exemplary apparatus employed in splat cooling the compositions of the invention;

FIG. 2 is a front elevational view of a toroidal inductor including a core material of the invention; and

FIG. 3 is a graphical representation on coordinates of relative frequency versus temperature in degrees Kelvin showing the variation in relative frequency as a function of temperature for toroidal inductors of the invention.

With reference now more particularly to FIG. l, there is shown in front elevational view an exemplary vertical gun apparatus capable of attaining quenching rates of the order of several million degrees per second and higher. The ligure shows a vertical gun 11, including a high pressure chamber 12 having a window 13 disposed therein, means 14 for introducing helium thereto and a Mylar diaphragm 15 at the lower extremity thereof, a low pressure chamber 16, means 17 for introducing argon there to, means 18 for RF heating said lower chamber, RF concentrators 19 and 20, and a water-cooled silver hearth member 21 having a 1/16 of an inch diameter hole 22 therein. A curved copper strip 23 is disposed beneath hole 22 for the purpose of receiving the molten material ejected during the process by means of a shock pulse.

In the operation of the splat-cooling process a suitable alloy is selected and placed upon the water-cooled silver hearth 21. For the purposes of the present invention, the alloys of interest are of the compositional range 45-65 weight percent cobalt, 10-20 weight percent vanadium, chromium, remainder iron. It has been found that deviation from these ranges results in the loss of the property of interest. An optimum has been found to correspond with those compositions including 50-53 weight percent cobalt, l2 weight percent chromium, remainder iron, and 52 weight percent cobalt, 14 Weight percent vanadium, remainder iron.

Prior to melting of the alloy, the lower end of the shock tube (low pressure chamber 16) is flushed with argon. Thereafter, with argon flowing through the lower chamber and over the alloy to prevent the adulteration thereof, power is supplied to heating means 18 to effect melting of the alloy. Next, helium is admitted into upper chamber 12 at a pressure of the order of 1000 lbs. per square inch, s0 resulting in rupture of diaphram 15 and ejection of the molten alloy at high velocity through hole 22 and the impingement thereof upon the copper strip.

With reference now to FIG. 2, there is shown in front elevational view an inductor utilizing a core material of the invention. Shown in the figure is core member 31 comprising a composition of the invention having Litz wire 32 wound thereon.

Examples of the present invention are set forth below:

EXAMPLE I An alloy comprising 14 percent, by weight, vanadium; 52 percent, by weight, cobalt, and 34 percent, iron were selected and placed upon the silver hearth of the apparatus shown in FIG. l. Thereafter, argon was admitted into the lower chamber and permitted to flush the system for a time period of one minute. Following, RF power was supplied to the heating means of the apparatus and the alloy heated above the melting temperature, at which time it was molten as noted visually. Then helium was admitted to the upper chamber of the apparatus at a pressure of approximately 1,000 l-bs. per square inch, thereby resulting in rupture of the Mylar diaphnagm and ejection of a molten drop of splat against the copper strip through the aperture in the lower extremity of the apparatus. The procedure described was used to fabricate a plurality of foils which were then removed from the copper and punched into rings with an outside diameter of Mt of an inch and an inside diameter of 1/s of an inch, the nominal thickness of the rings varying between 0.0015 inch and 0.003 inch. The rings so produced were next glued together under pressure with an epoxy cement, and the edges of the resultant torus were smoothed and Iwound with Litz wire. The inductance of the toroid was measured with a Tektronix L-C meter at room temperature, liquid nitrogen temperature, and liquid helium temperature to determine approximately the range of inductance variation. Toroids made in accordance with the procedure described above increased in inductance 15 times during cooling from room temperature to 4.2" K.

EXAMPLE II The procedure of Example I was repeated with the exception that an alloy comprising 13 weight percent vana- 3 dium, 52 weight percent cobalt, and 35 weight percent iron was employed. The resultant toroid increased more than 11 times in inductance during cooling from room tempertaure to 4.2 K.

EXAMPLE III The procedure of Example I was repeated with the exception of an alloy comprising 12 percent chromium, 52 percent cobalt, and 36 percent iron, was utilized. The resultant toroid increased in inductance 2 times during cooling from room temperature to 4.2 K., a maximum being reached between 77 K. and 4.2 K.

EXAMPLE IV A simple tunnel diode oscillator was assembled utilizing the composition fabricated in the manner described in Example I, the inductance of the toroid, placed in parallel with a capacitor, determining the generating frequency. The value of capacitance was chosen to adjust the frequency between 1 mHz. to 2 mHz. at room temperature.

This Was found to correspond to approximately the frequency range where the Q of the toroid peaked at room temperature, namely 26 at 1.5 mHz.

A toroidal inductor of the same composition as that utilized herein was placed in a Dewer flask and connected to the remaining components of the oscillator by an open core coaxial lead. The frequency was measured with a Hewlett Packard 5245L counter. The temperature of the toroidal inductor was varied by using a plurality of cryogenic fluids and at elevated temperatures by a heater block surrounding the inductor, temperature being measured by standard vapor pressure scales or a thermocouple in proximity to sample. In order to compare each of the toroids on a common basis, the frequency variation with temperature has been indicated as the relative frequency change as related to the observed frequency of each of the coils at 4.2 K. The observed frequencies for the coils of Examples I, II, and III, respectively, at 4.2 K. were 151.3, 523.7 and 909.5 kHz., respectively.

With reference now more particularly to FIG. 3, there is shown a graphical representation on coordinates of relative frequency versus temperature in degrees Kelvin, showing the variation in frequency for the toroids of Example I through III as a function of temperature. It will be noted by reference to the figure that all three toroids have a maximum frequency at high temperature, presumably where the superparamagnetic particles start transforming and a minimum at low temperatures. It has been theorized that the minimum is due to the fact that the materials experience antiferromagnetic coupling or that the magneto-crystalline anisotropy increases to a point lwhere the weak alternating induction is not sucient to wobble the spins.

What is claimed is:

1. Element comprising a mass of splat cooled alloy consisting essentially of 45-65 percent, by weight, cobalt, 10-20 percent, by weight, of an element selected from the group consisting of vanadium and chromium, remainder iron, together with means for sensing a temperature dependent change in magnetization of said mass.

2. Element in accordance with claim 1 wherein said mass is an inductor core and said sensing means is frequency sensitive.

References Cited UNITED STATES PATENTS 3,459,043 8/1969 Young 73k362 1,927,940 9/1933 Koster 75-123 K 2,350,329 6/1944 Hornfeck 73-362 CP 2,460,773 2/1949 Stimson 73-362 X 3,233,460 2/1966 Daunt et al 73-362 3,350,669 10/1967 DiLeo et al 73-362 X 3,421,374 1/1969 Wieting et al. 73-362 X FOREIGN PATENTS 1,077,381 7/1967 Great Britain 73-362 LOUIS R. PRINCE, Primary Examiner F. SHOON, Assistant Examiner U.S. Cl. X.R.

73-362 CP; 75-123 I, 123 K; 14S-31.55; 331-66 

